Study on the collision characteristics between high-temperature alumina droplets and char layer

The collision characteristics between high-temperature alumina droplets and the char layer in solid rocket motors are of great significance for the accuracy of slag deposition and flow-field simulations, however, the current research on the collision characteristics of the alumina droplets and char layer is still in a blank state. This study is based on the high-temperature molding method to prepare the char layer and compare the porosity with that of the char layer in solid rocket motors, indicating that the two are relatively similar in structure and can be applied to droplet impact experiments. An experimental study on the collision of alumina droplet with the char layer was conducted using a high-temperature alumina droplet impact experimental system. The experimental results show that the adhesion behavior of alumina droplets is related to the rough structure of the char layer and the high viscosity dissipation of the process of droplets impacting the char layer, and the droplets adhere during the retraction stage with violent oscillation. The rebound behavior of the droplets on the wall was characterized by “tail dragging”, “spinning” and “asymmetric rebound” phenomena due to the combination of high surface tension and the pinning effect of wall roughness. A regime map of the rebound/adhesion results of droplets impact the char layers was constructed. At the same speed, droplets with smaller particle sizes are more likely to adhere to the char layer. We established a relationship between the rebound and adhesion behavior. Based on the experimental results, the relationship for the maximum spreading factor of the droplets was established, providing a theoretical basis for the in-depth understanding and study of the droplet collision process in solid rocket motors.